1. Maya B. Mathur Castilleja School, Palo Alto, CA
Predictors of HPV Vaccination and Participation in Vaccination
Decision-Making
among High School Girls
Thank you
Good afternoon
Maya Mathur, senior at Castilleja School in Palo Alto
Two years ago, doctor recommended the HPV vaccine
Parents agreed.
I knew little about HPV and the vaccine, but went along.
New Scientist article describing the controversy catalyzed by the vaccine.
Since Gardasil’s approval by the Food and Drug Administration in 2006, some vocal parents, doctors, and lawmakers have supported immediately requiring all girls as young as 11 or 12 years old to receive the vaccine, while others have expressed concern for potential unknown side effects, infringement upon personal choice, or implicit approval of teenage sexual activity.
Maya B. Mathur
Castilleja School, Palo Alto, CA
CDC 43rd National Immunization Conference,
March 30 – April 2, 2009, Dallas, TX

2. Introduction
The public policy controversy over mandating the human papillomavirus (HPV) vaccine Gardasil has primarily involved opinions of politicians, healthcare professionals, and parents. However, attitudes and knowledge of girls themselves have not been examined.

3. Study Objectives To determine:
#1: to what extent high school girls are participating in vaccine decision-making.
#2: what sources of vaccine information high school girls use in their vaccine decision-making.
#3: the knowledge of high school girls about HPV and HPV vaccine-related knowledge
#4: the attitudes of high school girls towards mandatory vaccination.

4. Methods – 1 Design: Cross-sectional study
Target Population: Girls in grades 9 – 12 in the U.S.
Study Population: Girls in grades 9 – 12 from:
all-girls, private, non-sectarian school (Main Study)
co-educational public high school (Pilot Expansion Study)
(Both schools located in the San Francisco Bay Area)
Variables
Socio-demographic factors, attitudes, vaccine-related knowledge
Vaccination, participation in vaccination decision

5. Methods - 2 Sampling: Random, stratified by grade (Main Study)
Convenience sample (Pilot Expansion Study)
Survey Administration
59 multiple-choice and several write-in questions
Main Study: Anonymous online survey (N = 100)
Pilot Expansion Study: Paper surveys distributed by teachers for completion in science classes (N = 75)

6. Methods 3: Survey Development
Possible Source of Bias/Confounding
Action
Leading questions
Extreme care to develop balanced presentation
Use of feedback from pilot group
Gaining vaccine-related knowledge during survey
Use of decoy questions about other STDs and ovarian cancer
Priming events affecting attitudes and behavior
Questions that may result in “stereotype threat” (e.g., religion, parental education, school attended, frequency of doctor visits, etc.) appeared after questions about attitudes and knowledge

7. Summary of Survey Responses
Main Study
Pilot Expansion Study 75
distributed
100
distributed 95
returned 5
not returned 74
returned 1
not returned
Figure 1: Summary of Survey Responses. 81
completed 14
not completed 74
completed

8. Factors Associated with Vaccination

9. Percentage Vaccinated by Grade Level

10. Associations with Vaccination
Not associated with vaccination (p > 0.10)
Parental education
Post-HS plans
Estimate of HPV, warts, cervical cancer frequency
Frequency of doctor visits
Public co-ed school vs. private all-girls school
Associated with vaccination (p < 0.10)
Older age
Grade 11/12 (vs. 9/10)†
Attending religious services†
Info from MD or nurse
Higher knowledge score†
†p < 0.05, vaccinated vs. unvaccinated
main study

11. Vaccine Decision-Making

12. Participated in Vaccine Decision-Making

13. From What Source(s) Have you Heard About Gardasil?
(Main Study + Pilot Expansion Study)

14. Importance of Various Sources of Information in Decision-Making by Girls
% citing as important
N = 25 girls who participated in vaccine decision-making (main study)

15. Vaccine-Related Knowledge

16. Vaccine-Related Knowledge
12 multiple-choice factual questions
Total vaccine-related knowledge score: 0-12
3 write-in questions estimating risk
% of sexually-active people in US who have had an infection with HPV
% of sexually-active people in the US who have genital warts
% of women in the US get cervical cancer at some point in their lives

17. Vaccine-Related Knowledge Score (Main Study + Pilot Expansion Study)
% correct: % %

18. Can viruses cause cancer?
30-40% incorrect
(N = 66)
(N = 130)

19. Can men get infections with HPV?
50-60% incorrect
(N = 66)
(N = 130)

20. Can you get STDs after vaccination?
25-30% of unvaccinated girls got it wrong
(N = 66)
(N = 130)

21. What does Gardasil do for infection with HPV?
25-35% incorrect among unvaccinated girls
<100% of vaccinated girls knew this
(N = 66)
(N = 130)

22. What does Gardasil do for genital warts?
70% incorrect
(N = 66)
(N = 130)

23. What does Gardasil do for cervical cancer?
15-30% incorrect among unvaccinated
<100% correct among vaccinated
(N = 66)
(N = 130)

24. Estimates of Risk

25. Estimation of Risk of HPV and HPV-Related Conditions

26. Attitudes Towards Mandatory Vaccination

27. Agreement with Mandatory Vaccination
***
***
***
***p < Chi-Square agree/disagree/neutral

28. Conclusions and Implications
Implication(s) or Actions
H.S. girls frequently participate in HPV vaccine decision-making:
9/10th: 24%
95% CI [9%, 40%]
11/12th: 49%
95% CI [33%, 65%]
Good education of adolescent girls needed to ensure well-informed decisions
Girls’ knowledge of own behavior could be used to better risk-stratify
Target vaccine to those most at risk (health resource limitations)?
There are significant vaccine-related knowledge gaps
Target education based on known knowledge gaps (possible need for booster, STD still possible, etc.)
Girls rate parents, doctors, and own reading to be most important sources of information.
Disseminate information via sources girls rate as v. important to them

29. Limitations Cross-sectional design Associations, not causality
Without longitudinal evaluation, time sequence of attitudes and knowledge relative to vaccination cannot be known
Non-response bias
Generalizability
Pilot expansion study suggests generalization to wider population of high school girls than in the main study
However, future studies should aim to recruit subjects from a wider geographic range, more representative of the U.S. population

30. Thank you!